assume cs:codesg, ds:datasg
datasg segment
    db 'ibm .   .   .   ';16byte
    db 'dec .   .   .   '
    db 'dos .   .   .   '
    db 'vax .   .   .   '
datasg ends
codesg segment
    start: mov ax, datasg
            mov ds, ax

            mov bx, 0; 控制行
            
            mov cx, 4; 控制外层循环次数

        s:  mov dx, cx; 暂存本次循环的cx值
            mov cx, 3
            mov si, 0; 控制列
            s0: mov al, [bx+si]
                and al, 11011111B
                mov [bx+si], al
                inc si
                loop s0

            add bx, 16
            mov cx, dx
            loop s

            mov ax, 4c00h
            int 21h
codesg ends
end start